This invention relates to a rotary hammer, and particularly relates to a rotary hammer with a mode change mechanism for switching the rotary hammer for operation in any one of a hammer only mode, a rotary drive only mode and a rotary hammering mode.
In a hammer only mode of a conventional rotary hammer, a bit is inserted into a tool holder of the hammer and is repeatedly struck by a hammering mechanism and is not rotatably driven. In a rotary drive only mode, the bit is rotatably driven and is not subject to impacts from the hammering mechanism. In a rotary hammering mode, the bit is repeatedly struck by the hammering mechanism and is simultaneously rotatably driven.
Conventional rotary hammers of this type typically include a spindle mounted for rotation within a housing of the hammer which can be driven by a rotary drive arrangement, selectively engageable and disengageble with a pinion driven by a motor of the hammer. The spindle rotatably drives a tool holder of the hammer which in turn rotatably drives a tool or bit releasably secured within the hammer. A piston is generally slideably located within the spindle and is reciprocally driven by a hammer drive mechanism which translates the rotary drive of a hammer motor to a reciprocating drive of the piston. A ram, also slideably located within the spindle, forward of the piston, follows the reciprocation of the piston due to successive reversing pressures in an air cushion within the spindle between the piston and the ram. The ram repeatedly impacts an anvil slideably located within the spindle forward of the ram which transfers the forward impacts from the ram to the tool or bit, for limited reciprocation within the tool holder at the front of the hammer. The mode change mechanisms for such hammers can selectively engage and disengage the rotary drive to the spindle and the reciprocating drive to the piston.
In a known type of mode change mechanism, a single mode change actuator is used to switch the hammer between different modes. However, mechanisms of this type tend to be relatively complex, use parts which are intricate and/or difficult to manufacture inexpensively in bulk, with sturdy qualities that can withstand sustained use of the hammer, and/or are relatively difficult to assemble.
A known mode change arrangement is disclosed in U.S. Pat. No. 5,159,986, and includes a mode change knob having a first cam element for activating and de-activating hammering, and a second cam for activating and deactivating rotary drive. The disclosed arrangement also includes the option of operating at either of two drive speeds. In a first position of the first cam element, rearward movement of the spindle is blocked, which prevents the drive from being transmitted to the hammer drive arrangement. In a second position of the first cam, rearward movement of the spindle occurs when the tool or bit is pressed against a work surface. This rearward movement of the spindle results in the engagement of two coupling parts which allows the drive to be transmitted from an intermediate shaft to the hammer drive arrangement.
The second cam arrangement, as described in U.S. Pat. No. 5,159,986, is used to guide an adjustment element along a rod mounted in the housing of the hammer, which adjustment element engages spindle drive gears to shift the gears between three positions. In a first of the three positions, a drive gear engages a spindle lock to prevent rotation of the spindle, and relates to of a surface of the first cam whereby drive is transmitted to the hammer drive arrangement. In a second position, a first drive gear engages the intermediate shaft to drive the spindle at a first speed of rotation, and, in a third position, a second drive gear engages the intermediate shaft to drive the spindle at a second speed. The three positions of the drive gears, as they relate to the orientation of the second cam element, are co-ordinated with the blocking and non-blocking positions, in relation to the orientation of the first cam element, in order to co-ordinate the activation of the spindle at the required speed with the activation of hammering.
The mode change arrangement as disclosed in U.S. Pat. No. 5,159,986 requires many non-standard type parts such as the first and second cam surfaces, an adjustment element, a bearing and a cage, which have to interact to change between the modes of operation. Such parts are relatively expensive to manufacture in such a way that the parts can survive sustained use of the hammer and still provide smooth changes between the different modes of operation of the hammer. Also, the assembling of the parts to provide such a mode change arrangement is relatively difficult, which further adds to the cost of manufacturing such hammers. Further, a biasing means between the knob and the adjustment element is required to bias the gears or teeth into position for meshing until one of the gears has rotated sufficiently to allow actual meshing to occur. This results in additional cost and complexity.
Therefore, it is an object of this invention to provide a rotary hammer having a simple and reliable mode change mechanism for selectively operating in a hammer only mode, a rotary hammer mode, or a rotary drive only mode.
Another object of this invention is to provide a rotary hammer having a mode change mechanism which utilizes primarily standard engineering parts such as splined shafts, gear wheels, splined sleeves and springs.
A further object of this invention is to provide a rotary hammer having a mode change mechanism which utilizes primarily standard engineering parts which are sturdy and inexpensive to manufacture, and relatively easy to assemble.
With these and other objects in mind, this invention contemplates a rotary hammer, which includes an intermediate shaft rotatably drivable by a motor, and a spindle which can be driven about an axis thereof by the intermediate shaft through a spindle drive arrangement. The rotary hammer further includes a tool holder arranged for rotation with the spindle for releasibly holding a bit or a tool for reciprocation, a pneumatic hammering arrangement located within the spindle which can repeatedly impact the bit or tool held within the tool holder. The pneumatic hammering arrangement includes a piston which can be reciprocally driven by a hammer drive arrangement for translating rotary drive from the intermediate shaft to a reciprocating drive for the piston. The rotary hammer further includes a mode changing mechanism for changing the operation of the hammer amongst a hammer only mode, a rotary hammer mode, and a rotary drive only mode. The mode change mechanism includes a spindle driving member rotatably mounted on the intermediate shaft for driving the spindle drive arrangement, a hammer driving sleeve rotatably mounted on the intermediate shaft for driving the hammer drive arrangement, and a mode change sleeve, which surrounds the intermediate shaft and which is permanently driven by and shiftable along the intermediate shaft. The switching of the actuator by a user shifts the mode change sleeve along the intermediate shaft to any one of three positions, such that, in a first rotary drive only position, the mode change sleeve transmits rotary drive to the spindle driving member and to transmit rotary drive to the spindle drive arrangement. In a second hammer only position, the mode change sleeve transmits rotary drive to the hammer driving sleeve to transmit rotary drive to the hammer drive arrangement. In a third rotary hammer position, the mode change sleeve transmits rotary drive to the spindle driving member and to the hammer driving sleeve to transmit rotary drive to the spindle drive arrangement and to the hammer drive arrangement.
This invention further contemplates the mounting of the hammer drive sleeve and the spindle drive member rotatably on the intermediate shaft, and the mounting of the mode change sleeve shiftably and non-rotatably along the intermediate shaft. This facilitates use of the mode change sleeve to transfer rotary drive from the intermediate shaft to the hammer drive sleeve and/or the spindle drive member by simply shifting the mode change sleeve along the intermediate shaft to selectively engage the hammer drive sleeve and/or the spindle drive member. The parts required for this mode change mechanism are standard engineering parts, such as a shaft and sleeves rotatable or non-rotatable on the shaft and optionally shiftable along the shaft. The sleeves have parts such as gear wheels or teeth, which are selectively engageable with each other. Such parts can be manufactured inexpensively and of sturdy structure, and can be easily assembled to provide a simple and reliable mode change mechanism.
In further contemplation of this invention, preferably, an intermediate shaft driving member, preferably a gear which is non-rotatable on the intermediate shaft, is in permanent engagement with a mode change sleeve driven member, preferably a set of teeth on the mode change sleeve, so that rotation of the intermediate shaft rotatingly drives the mode change sleeve.
Still, in further contemplation of this invention, in a preferred arrangement, the hammer drive sleeve is located towards the rear of the mode change sleeve and has a driven member, preferably a set of teeth, which is engageable with a driving member, also preferably a set of teeth, on the mode change sleeve to transmit rotary drive from the intermediate shaft to the hammer drive sleeve. Preferably, the mode change sleeve driven member, which engages the intermediate shaft driving member, is axially extended and also forms the mode change sleeve driving member, which is engageable with the hammer drive sleeve driven member, to transmit rotary drive from the intermediate shaft to the hammer drive arrangement. Using a single extended driven and driving member, such as an extended set of teeth, again simplifies the structure of the mode change sleeve.
This invention also contemplates, in a preferred arrangement, the spindle drive member being located towards the front of the mode change sleeve and has a driven member, preferably a set of teeth, on the mode change sleeve to transmit rotary drive from the intermediate shaft to the spindle drive member. Again, it is preferred that the mode change sleeve driven member which engages the intermediate shaft driving member is axially extended to also form the mode change sleeve driving member which is engageable with the spindle drive member to transfer rotary drive from the intermediate shaft to the spindle drive member. Using a single extended driven and driving member, such as an extended set of teeth, again simplifies the structure of the mode change sleeve.
The spindle drive member may be a spindle drive sleeve which is rotatably mounted on the outside of the intermediate shaft. Alternatively, the spindle drive member may be a spindle drive pinion which is rotatably mounted within the front end of the intermediate shaft.
When the above preferred arrangements are both used on the hammer, the mode change mechanism is arranged such that, in a first rotary drive only position, the mode change sleeve is shifted to a forward position on the intermediate shaft to transmit rotary drive to the spindle driving member by way of the mode change sleeve driving member and the spindle drive member driven member. In a second hammer only position, the mode change sleeve is shifted to a rearward position on the intermediate shaft to transmit rotary drive to the hammer driving sleeve by way of the mode change sleeve driving member and the hammer drive sleeve driven member. In a third rotary hammer position, the mode change sleeve is shifted to an intermediate position on the intermediate shaft between the forward and rearward positions and transmits rotary drive to the spindle driving member and transmits rotary drive to the hammer driving sleeve.
In a preferred embodiment, the switching of the single actuator shifts the mode change sleeve by way of a mode change member. The mode change member may be mounted on a housing part of the hammer so as to be slideable in a direction substantially parallel to the intermediate shaft. The mode change member is preferably provided with a mode change arm, preferably a ring, which extends laterally of the mode change member. The mode change arm at least partly surrounds at least a part of the mode change sleeve and is connected to the mode change sleeve such that shifting of the mode change member shifts the mode change sleeve by way of the mode change arm amongst the three positions.
In order to insure transmission of rotary drive between the parts, which may not initially be in meshing alignment when the hammer is first switched to one of the three modes of operation, a biasing arrangement is located between the actuator and the mode change sleeve in order to bias the sleeve towards a position on the intermediate shaft which corresponds to the position to which the actuator is switched. When the hammer includes a mode change member having a mode change arm as described above, it is preferred that the biasing arrangement include a first spring means located between a forward end of the mode change sleeve and a forward facing part of the mode change arm and a second spring means located between a rearward end of the mode change sleeve and a rearward facing part of the mode change arm.
Preferably, a spindle lock is provided on the hammer to lock the spindle against rotation when the hammer is in the hammer only mode. When the hammer includes a mode change member, as described above, it is preferred that the spindle lock include a first locking means located on the mode change member, which first locking means is engageable with a second locking means provided on the spindle when the mode change member is shifted to a hammer only mode position to lock the spindle against rotation.
The actuator may be a rotatable knob mounted on a housing part of the hammer such that the rotation of the knob rotates an eccentric pin which pin is slideably engaged, preferably with a slot in the mode change member, in order to shift the mode change member and thereby shift the mode change sleeve amongst the three mode positions.
The mode change mechanism described above is suited to the type of hammer having a pneumatic hammering arrangement which includes a reciprocally driven piston, which reciprocally drives a ram by way of a closed air cushion. The ram repeatedly impacts an anvil which is driven, in a forward direction, to impact a bit or tool held in the tool holder. This arrangement is particularly suited to the type of hammer in which the intermediate shaft is substantially parallel to the spindle.
It is preferred that the spindle drive member include a driving member. preferably a gear, which is in permanent engagement with the spindle drive engagement, which preferably includes a gear.
It is also preferred that the hammer drive arrangement is a wobble plate drive arrangement.
Preferably, a releasable detent arrangement is provided for releasably latching the actuator in the required mode switch position. This is important if the hammer includes means for biasing the mode change mechanism into meshing engagement when the meshing parts are initially not aligned.
Other objects, features and advantages of the present invention will become more fully apparent from the following detailed description of the preferred embodiment, the appended claims and the accompanying drawings.